1 There is some other expense you can save significantly on by DIY. An example would be DIY k8s on bare metal via bare metal providers for a massively bandwidth intensive service where paying AWS or GCP outbound data rates would be thousands and thousands a month.
2 You are at sufficient scale that there is an economy of scale that can be accessed. This overlaps a bit with the first point but can also happen if you are just big enough. The first point is more about some special need.
1 There is some other expense you can save significantly on by DIY. An example would be DIY k8s on bare metal via bare metal providers for a massively bandwidth intensive service where paying AWS or GCP outbound data rates would be thousands and thousands a month.
2 You are at sufficient scale that there is an economy of scale that can be accessed. This overlaps a bit with the first point but can also happen if you are just big enough. The first point is more about some special need.